Product Review: Modular Homes

Modular homes combine factory efficiency with building science expertise to achieve new levels of performance.

You may be surprised to learn that the very first house to achieve Platinum-level certification under the USGBC’s LEED for Homes program was a modular home installed in Santa Monica, Calif., by LivingHomes in 2006. Since then, factory home builders have made it a point to be the first in their respective markets to attain high-level green certifications from basic, Bronze-level ANSI National Green Building Standard (NGBS) to Passive House, including many net-zero homes and communities.

“The prefab industry embraced green building to meet growing demand, showcase their products, and, because the efficiencies inherent to factory production—including rigorous quality control, resource conservation, and the ability to assemble a house from the inside out—provide factory home builders with advantages difficult to match, even by the best green builders constructing on-site,” says Sheri Koones, author of Prefabulous + Sustainable.

To a significant degree, green building depends on critical construction details, such as accurate sealing, flashing, and insulation. Working in a climate-controlled environment that resembles a cabinet shop more than a construction site, technicians and craftsmen labor comfortably on all levels of a structure, from floors to roof, without balancing on ladders, enduring harsh weather, or straining their backs.

“The ergonomics of a factory setting favor high-quality workmanship, which is the first principle of green building,” says Steve Glenn, whose company, LivingHomes, strives to build homes certified as LEED-Platinum. Glenn turned to the modular approach to ensure strict and consistent architectural compliance, project after project.

Many developers and architects are finding that quality and cost favor the modular approach for their high-performance projects. But before delving into all the reasons you may want to consider modular construction for your next high-performance home or addition, we should go over some basic prefab vocabulary since the terms “manufactured” and “modular” are not synonymous and often are misapplied.

Manufactured housing refers to factory-built homes meeting the National Manufactured Housing Construction and Safety Standards, developed and enforced since 1974 by HUD. Commonly known as the HUD-Code, this national standard makes it possible for the industry to build and sell homes across jurisdictional boundaries without having to meet myriad state and local codes.

Manufactured homes are typically single story and trucked to the site in one to three sections, each constructed on a steel frame with wheels, making it possible to relocate the unit. Designed as affordable housing, manufactured homes often carry the Energy Star Qualified label when produced and installed in accordance with Energy Star’s guidelines by a certified plant. Some manufacturers, such as Dallas-based Palm Harbor, will also build models that qualify for green building certifications, including LEED, NGBS, Earth Advantage, and others. Although common with higher-end modular homes, costly certifications remain rare in HUD-Code models.

Modular homes are also constructed in one or more three-dimensional factory units, but to state and local codes rather than a federal standard. The modules are transported to the home site for assembly on a permanent foundation. A network of authorized, surrogate state inspectors review plans and visit the modular factory for compliance inspections during the manufacture of each home. Green certification inspections, including Energy Star, LEED, and NGBS, are also performed by specialized third-party inspectors. The final, on-site inspection is done by a local HERS rater, just as with any other certified home.